Thermodynamic measurements will be made on lipid bilayer systems and biomembranes. The measuring techniques are differential scannig dilatometry (DSD), using a state of the art instrument constructed under a previous grant, and differential scanning caloriemetry (DSC), using a recently acquired Microcal device. These measurements together with elementary theory provide estimates of intermolecular interactions and the change sn rotameric disorder, especially at phase transitions, although our efforts are also being directed to measuring the specific heat and the coefficient of expansion in single phase regions as well. It is proposed to study a variety of system ranging from highly pure single component lipid bilayers, through binary mixtures which more closely simulate biomembranes and which exhibit rich phase diagrams, to biomembranes such as the purple membrane and frog sciatic nerve.